In order to correct an error in an image position when an image forming section of an image forming apparatus forms an image, there is a known method of repeating an image forming process with respect to a reference image stored in a memory within the image forming apparatus, and a task of inputting a correction value by the user. In this technique, the user visually compares an output image which is formed and output by the image forming apparatus performing an image forming process with respect to the reference image, with the reference image, to measure an error in the image position, inputs into the image forming apparatus a correction value which is considered to be appropriate for correction of the measured error, and thereafter, causes the image forming apparatus to perform an image forming process with respect to the reference image. The user repeats this procedure until the error falls within a tolerable range. Therefore, the user needs to not only determine a correction value in consideration of the measurement result of an error, but also repeat the image forming process with respect to the reference image until the error falls within the tolerable range, resulting in a waste of resource and a longer time required for the task.
To avoid this, there is a conventional image forming apparatus that detects a difference between the image position of an output image of an original image and the image position of the original image, and adjusts a draw start position of an image on a laser exposing apparatus (see, for example, Patent document 1). Note that the draw start position is stored in the image forming apparatus.
When the reference image read from a read original by an image reading section is compared with an output image formed by the image forming section with respect to the reference image, errors in an image position and an image scaling factor of an output image with respect to the reference image (read original) are caused by, specifically, errors in an image read position and an image read scaling factor when an image is read in the image reading section, and errors in an image formation position and an image formation scaling factor when an image is formed in the image forming section. In other words, the errors in the image forming section of the image forming apparatus and the errors in the image reading section of the image forming apparatus are combined to provide the errors in the image position and the image scaling factor as a whole.
To avoid this, there is another conventional image forming apparatus that reads a predetermined reference image in an image reading section and calculates a correction value for an image read scaling factor, and thereafter, performs image formation with respect to a reference image in an image forming section to create an output image, and causes the image reading section to read the output image and calculating a correction value for an image formation scaling factor (see, for example, Patent document 2). This image forming apparatus calculates an error in the image forming section and an error in the image reading section of the image forming apparatus, separately.
However, in the image forming apparatus of Patent document 1, the image read position error in the image reading section and the image formation position error in the image forming section are not separated. Therefore, when one of the image forming section and the image reading section is not used, the image position error and the image scaling factor error cannot be accurately corrected.
In the image forming apparatus of Patent document 2, even when one of the image forming section and the image reading section is not used, the image position error and the image scaling factor error can be accurately corrected. However, it is necessary to read both the reference image and the output image in the image reading section, resulting in a complicated task of correcting the image position and the image scaling factor.
Further, there is an image forming apparatus capable of selectively performing a fixed original type image reading process of reading an image by scanning an original placed on an original platen using an optical system of an image reading section, the optical system being provided facing the original platen, and a moving original type image reading process of reading an image of an original which is being transferred and moved, where an optical system of an image reading section is provided facing the original via the original platen. In such an image forming apparatus, an error occurring in the image reading section during the fixed original type image reading process and an error occurring in the image reading section during the moving original type image reading process need to be corrected separately. Therefore, in the image forming apparatus of selectively performing the fixed original type image reading process and the moving original type image reading process, the task of correcting the image position and the image scaling factor is more complicated.
An object of the present invention is to provide an image position correcting method, an image position correcting instrument, and an image forming apparatus capable of correcting errors in an image read position and an image read scaling factor in an image reading section and errors in an image formation position and an image formation scaling factor in an image forming section, separately, by performing an image reading process once and an image forming process once, thereby making it possible to perform a task of accurately correcting an image position and an image scaling factor simply and quickly.
Another object of the present invention is to provide an image position correcting method and an image forming apparatus capable of correcting errors in an image read position and an image read scaling factor in an image reading section during each of a fixed original type image reading process and a moving original type image reading process, and errors in an image formation position and an image formation scaling factor in an image forming section, separately, by performing a fixed original type image reading process, a moving original type image reading process, and an image forming process once for each, thereby making it possible to perform a task of accurately correcting an image position and an image scaling factor simply and quickly.
Patent document 1: JP H10-186994 A
Patent document 2: JP H08-265560 A